If you are having issues with the PS Vita battery not charging or running down quickly, try the following:

Are you playing something while the PS Vita system is charging?
If you are playing something while the PS Vita system is charging, the charging time will take longer than when you are not playing anything.

Did you turn off the PS Vita system when charging it using a USB cable?
The PS Vita system can also be charged by connecting it to a USB device such as a PC. In this case, be sure to turn off the PS Vita system before charging it.

Did you press and hold the power button to turn off the system?
Although a quick press puts your system into standby mode, it does not turn the system off.
When you will not use the system for a long time, press the power button for 2 seconds and then tap [Power Off] on the screen that appears to turn off the system.

Is the AC adaptor connected properly and charged enough? Connect the USB cable so that the PS logo is visible along with the PS Vita logo below the system screen (touchscreen).

Does the PS button light up orange when the AC adaptor is connected?

PS button is blinking
The battery has no remaining charge.
Wait until the PS button stops blinking and lights up orange before pressing the power button.

PS button does not light up
The AC adaptor or battery may be defective.
You will need to send your system in for service. Click here for service information.